Some vehicles, such as aircraft, include panels having cells. For example, a panel may be composed of a honeycomb core sandwiched between two facesheets. More specifically, interior cell walls of the honeycomb core are perpendicular to the facesheets. In some situations, the cell walls of the core may move out of perpendicular orientation with the facesheets. The angle between a cell wall and one of the facesheets is referred to as the shear angle. If the shear angle is zero, the cell wall is perpendicular to the facesheet.
Currently, in order to measure the shear angle, the panel is sliced into pieces. Each piece is then examined to determine if the shear angle is greater than zero. Typically, the shear angle is measured by hand. If the shear angle is greater than zero, the forming process for the panels can be adjusted to produce a zero shear angle. Measurements of subsequent panels and further adjustments to the forming process may be made in order to eventually achieve a zero shear angle between the cell walls of the core and the facesheets.
In addition, non-destructive inspection of the panel may be performed using an X-ray system. However, current X-ray inspection techniques are unable to measure the shear angle between the cell walls and the facesheets. Particularly, if the X-ray system collects image data of the core from a view normal to the facesheet, a nonzero shear angle appears the same as a zero shear angle in an image generated from the collected data. Moreover, if the X-ray system collects image data of the core from a view parallel to the facesheet, the X-rays cannot transmit through the entire length of the panel, and thereby cannot produce an X-ray image.
Accordingly, there exists a need for a non-destructive inspection technique that determines the shear angle in the interior of the panels having cells.